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For anyone that has participated in one of The Bonsai Site's surveys or who has
consulted a reference on growing conditions for particular plants, they have
most probably encountered the mention of 'zones'. Since hardiness or tolerance
to cold extremes is a primary consideration for farming and gardening in much of
the US, the United States Department of Agriculture (USDA) has, since 1960,
maintained and published temperature data for the North American continent.
Using this data, the continent was divided into twenty zones separated by 5
degree F differences.
This measurement is now applied internationally - although there are notable differences between the regions.
Reproduction in whole or in part in any form or medium without express written permission of The Bonsai Site is prohibited. |
